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Methods of operating needle-free injection device having an outer housing
and an inner housing is disclosed. The inner housing is configured to
receive a needle-free syringe in one end. In addition, the inner housing
is movable within the outer housing between a syringe loading position
and a firing position. The device may include an activation button
operatively associated with the inner and outer housings and a housing
lock engaged by the activation button to prohibit movement of the inner
housing from the syringe loading position to the firing position when the
activation button is activated with the inner housing in the syringe
loading position.

1. A method of operating a needle-free injector comprising: providing a
needle-free injector comprising an outer housing, an inner housing
moveable within the outer housing between a syringe loading position and
a firing position, an activation button operatively associated with the
inner and outer housing, and a housing lock engaged by the activation
button; activating the activation button when the inner housing is in the
syringe loading position to lock the inner housing in the syringe loading
position; and loading a needle-free syringe into the needle-free
injector.

2. The method of claim 1 further comprising: releasing the activation
button while the inner housing is in the syringe loading position; moving
the inner housing to the firing position; and triggering the delivery of
a fluid injection by activating the activation button when the inner
housing is in the firing position.

3. The method of claim 2 further comprising: providing the needle-free
injector with an eject button which is separate from the activation
button; and ejecting the needle-free syringe from the needle-free
injector by activating the eject button.

4. The method of claim 3 further comprising preventing activation of the
eject button when the inner housing is moved from the syringe loading
position toward the firing position.

5. The method of claim 3 further comprising: providing the needle-free
injector with an extension on the outer housing that at least partially
shields the eject button when the inner housing is moved from the syringe
loading position toward the firing position; and preventing activation of
the eject button with the extension, when the inner housing is moved from
the syringe loading position toward the firing position.

6. The method of claim 3 further comprising providing the needle-free
injector with a syringe eject spring providing sufficient force to
completely eject a needle free syringe away from any contact with the
needle-free injector upon activation of the eject button.

7. The method of claim 1 further comprising preventing the loading of the
needle-free syringe into engagement with a syringe mount at one end of
the inner housing, unless the inner housing is in the syringe loading
position.

8. The method of claim 1 further comprising causing the inner housing to
move from the syringe loading position toward the firing position by
applying force to a nozzle end of the needle-free syringe.

9. The method of claim 1 further comprising preventing the removal of the
needle-free syringe from engagement with a syringe mount at one end of
the inner housing, unless the inner housing is in the syringe loading
position.

10. The method of claim 1 further comprising preventing the inner housing
from being moved from the syringe loading position to the firing position
if the syringe is not properly loaded in a syringe mount at one end of
the inner housing.

11. A method of operating a needle-free injector comprising: providing a
needle-free injector comprising an outer housing, an inner housing
moveable within the outer housing between a syringe loading position and
a firing position, and a syringe mount; and loading a needle-free syringe
into the syringe mount, wherein the syringe mount prevents the placement
of the needle-free syringe into engagement with the syringe mount unless
the inner housing is in the syringe loading position.

12. The method of claim 11 further comprising causing the inner housing
to move from the syringe loading position toward the firing position by
applying force to a nozzle end of the needle-free syringe.

13. The method of claim 11 further comprising preventing the removal of
the needle-free syringe from engagement with the syringe mount, unless
the inner housing is in the syringe loading position.

14. The method of claim 11 further comprising preventing the inner
housing from being moved from the syringe loading position to the firing
position if the syringe is not properly loaded in the syringe mount.

15. A method of operating a needle-free injector comprising: providing a
needle-free injector comprising an outer housing, an inner housing
moveable within the outer housing between a syringe loading position and
a firing position, a syringe mount, and an eject button; loading a
needle-free syringe into the syringe mount; and ejecting the needle-free
syringe from the needle-free injector by activating the eject button.

16. The method of claim 15 further comprising preventing activation of
the eject button when the inner housing is moved from the syringe loading
position toward the firing position.

17. The method of claim 15 further comprising: providing the needle-free
injector with an extension on the outer housing that at least partially
shields the eject button when the inner housing is moved from the syringe
loading position toward the firing position; and preventing activation of
the eject button with the extension, when the inner housing is moved from
the syringe loading position toward the firing position.

18. The method of claim 15 further comprising providing the needle-free
injector with a syringe eject spring providing sufficient force to
completely eject a needle free syringe away from any contact with the
needle-free injector upon activation of the eject button.

Description

RELATED APPLICATIONS

[0001] This application is a divisional application of U.S. patent
application Ser. No. 13/196,419 filed Aug. 2, 2011, entitled "Needle-Free
Injection Device," which is incorporated herein in its entirety by
reference for all matters disclosed therein.

TECHNICAL FIELD

[0002] The embodiments disclosed herein relate generally to needle-free
injection devices and methods of injecting serums, medicine, inoculants
or other injectable fluid into or through the skin of a human or animal.

BACKGROUND

[0003] The advantages of needle-free injection devices have been
recognized for some time. Some of the advantages of needle-free devices
and methods include the absence of a needle which can intimidate a
patient and also present a hazard to healthcare workers. In addition,
injection using a needle may increase the risk of cross-contamination
between patients. Furthermore, with an injection device that employs a
needle there is substantial risk of needle breakage in the tissue of a
human or animal patient. The injection jet generated by a needle-free
device is generally smaller in diameter than a hypodermic needle and thus
in certain instances a needle-free injection is less painful than an
injection provided by a hypodermic needle device.

[0004] Because of these and other advantages of needle-free injection many
variations of pneumatic, electronic or spring activated needle-free
injection devices have been designed to provide a single injection, or
alternatively a series of injections to one or more patients. Most known
needle-free injection devices operate by driving the injectable fluid
through a fine nozzle with a powered piston to create a fine but high
pressure jet of fluid that penetrates the skin. Needle free injection
devices are not inherently risk free. For example, it is possible if
precautions are not taken, to cause a laceration as opposed to a proper
injection with a needle-free device. In addition, it is critical to
design a needle-free device with safety features substantially minimizing
the risk of inadvertent triggering or injection.

[0005] Thus, a great deal of attention has been given to the development
of needle-free injection devices and methods which are safe, reliable and
easy to use in the field. Needle-free technologies raise certain unique
engineering challenges which are likely to be encountered when designing
a suitable device. For example, conventional needled syringes are often
inexpensive or disposable devices. Thus a large supply of pre-filled
syringes can be prepared for large scale inoculation projects. On the
other hand, needle-free devices are typically more expensive since these
devices require a relatively sophisticated pneumatic, electronic or
spring power source, energizing system and triggering system. Although a
needle-free device can be designed to accept disposable (or recyclable)
needle-free syringes, it can be difficult to quickly and accurately load
a pre-filled needle-free syringe into an injection device, particularly
without contaminating the injection nozzle. Similarly, it can be
difficult to remove a spent needle-free syringe and replace same with an
unused syringe quickly, efficiently and in a sterile manner. Thus, known
needle-free injection devices can be difficult to use for large scale
inoculation projects or in other situations where a significant number of
injections are made to a relatively large group of patients.

[0006] Safety issues may involve the risk of accidental discharge of a
needle-free device. Safety issue can become acute in association with
devices that have exposed triggers or devices which include a ram or
piston driving mechanism that can extend beyond the housing of the
injector. The risk of using these types of devices is similar to the
risks associated with the triggers on firearms. Thus, the inadvertent
pressing of an exposed and armed trigger can cause the accidental or
premature firing of the needle-free injection device.

[0007] One class of reliability issue with known needle-free injection
devices involves difficulty delivering an entire preselected dosage of
injectable liquid into the appropriate tissue of a patient. Dosage
reliability issues have a broad spectrum of causes. One significant
underlying cause is the difficulty encountered in the creation of a
suitable jet or stream of fluid and introduction of this jet into or
through the skin of a patient. Preferably, the jet will be a very fine
jet that will impact a section of taught skin with much of the energy of
the stream being used to penetrate the skin. The elasticity and
permeability of a patient's skin can however vary with respect to other
patients or across different locations on a patient's body. Another
reliability issue concerns difficulty encountered efficiently and
accurately pre-filling needle-free syringes to a selected dosage without
significant waste of a potentially very limited supply of injectable
fluid.

[0008] The embodiments disclosed herein are directed toward overcoming one
or more of the problems discussed above.

SUMMARY OF THE EMBODIMENTS

[0009] One embodiment includes a needle-free injection device having an
outer housing and an inner housing. The inner housing is configured to
receive a needle-free syringe in one end. In addition, the inner housing
is movable within the outer housing between a syringe loading position
and a firing position. This embodiment also includes an activation button
operatively associated with the inner and outer housings and a housing
lock engaged by the activation button to prohibit movement of the inner
housing from the syringe loading position to the firing position when the
activation button is activated with the inner housing in the syringe
loading position.

[0010] Generally, a syringe loading position is defined for any device as
a configuration between inner and outer housings where syringe loading or
syringe ejection is enabled and injection operations are substantially
prohibited. In addition, for any device, a firing position is defined as
a configuration between inner and outer housings where injection is
enabled.

[0011] The housing lock of the above embodiment may be implemented with
any suitable mechanism which serves to lock the inner housing in the
syringe loading position with respect to the outer housing. For example,
the housing lock can include an engagement surface on the activation
button that mates with a corresponding recess on the inner housing.

[0012] In certain embodiments, the needle-free injection device further
includes a powered hammer within the inner housing communicating with a
plunger within a needle-free syringe. The hammer is released with a
release mechanism to provide stored energy to the plunger to power an
injection. Furthermore, the activation button is configured to only
engage the release mechanism when the housing is in the firing position.
Thus, in this embodiment, the activation button has at least two distinct
functions. The activation button operates to lock the needle-free
injection device in the syringe loading position when it is depressed or
otherwise activated while in the syringe loading position and the same
activation button operates to trigger the device and release stored
energy to power the hammer, thus causing an injection, if the activation
button is activated with the inner housing in the syringe loading
position.

[0013] The release mechanism may be implemented with any suitable
mechanism. For example, the release mechanism can comprise a lever
associated with the activation button and a ball lock sleeve associated
with the lever and the hammer such that articulation of the lever moves
the ball lock sleeve thereby releasing the hammer. The hammer may be
powered by any suitable pneumatic, spring, electronic or other power
source.

[0014] In some embodiments, the needle-free injection device further
includes a syringe mount to receive a needle-free syringe at one end of
the inner housing. The syringe mount comprises an interlocking structure
cooperating with the inner housing and outer housing to prevent the
placement of a needle-free syringe into engagement with the syringe mount
unless the inner housing is in the syringe loading position. The syringe
mount and associated interlocking structure may be implemented with any
suitable components, for example, the syringe mount and interlocking
structure can comprise at least one rotating pawl providing for
engagement with the needle-free syringe. A tab is provided toward the
exterior of at least one pawl and a corresponding opening is provided
through the inner housing. In addition, a corresponding space is provided
within the outer housing such that the pawl can rotate to receive a
syringe only if the opening through the inner housing is aligned with the
space within the outer housing, for example, when the inner housing is in
the syringe loading position. Alternatively, the pawl may be prohibited
from rotating if the inner housing is not in a syringe loading position
by tab interference with a corresponding portion of the outer housing.

[0015] The interlocking structure can also be configured to engage with
the inner housing after a needle-free syringe is loaded such that force
applied to a nozzle end of the needle-free syringe causes the inner
housing to move from the syringe loading position toward the firing
position. In addition, the interlocking structure can cooperate with the
inner housing and outer housing to substantially prevent the removal of a
needle-free syringe from engagement with the syringe mount unless the
inner housing is in the syringe loading position. Furthermore, the
interlocking structure can cooperate with the inner housing and outer
housing to prevent the inner housing from being moved from the syringe
loading position to the firing position if a syringe has been improperly
loaded in the syringe mount.

[0016] Embodiments of the needle-free injection system further comprise an
eject button associated with the syringe mount such that activation of
the eject button causes the syringe mount to release a previously mounted
needle-free syringe. Inadvertent syringe ejections are substantially
prevented by providing an extension on the outer housing that at least
partially shields the eject button when the inner housing is moved from
the syringe loading position toward the firing position. In addition, the
interlocking structure can prevent ejection unless the inner housing is
in the syringe loading position. The system may optionally be provided
with a syringe eject spring which provides sufficient force to completely
eject a needle-free syringe away from any contact with the needle-free
injection system upon activation of the eject button.

[0017] The needle free injection system may also comprise a needle-free
syringe. The needle-free syringe may include at least two raised surfaces
on the syringe body defining at least one orientation channel configured
to mate with an orientation structure of the syringe mount. The syringe
may further include a grip edge defined at least in part by the raised
surfaces which engages the syringe mount when a needle-free syringe is
mounted. The foregoing structures may be implemented to allow the
mounting of a needle-free syringe without requiring rotation the syringe
body or syringe mount to lock the syringe to the syringe mount.
Furthermore, the foregoing structures and associated syringe mount and
ejection structures may provide for the mounting, use and subsequent
ejection of a needle-free syringe from the system without requiring that
the syringe be touched or grasped by an operator's hand at any step of
the process.

[0018] The foregoing embodiments of needle-free injection systems are
described as including a multi-purpose activation button, housing lock
and release mechanism subsystem, a syringe mount and interlocking
structure subsystem and various features associated with a suitable
needle-free syringe itself. Alternative device embodiments may include
any combination of one or more of the foregoing subsystems or structures.

[0019] An alternative embodiment is a needle-free syringe comprising a
syringe body having a nozzle at one end and a dose setting surface
substantially opposite the nozzle. The needle-free syringe further
includes a plunger body having a leading end, a seal and a hammer surface
substantially opposite the leading end. In this configuration, the
syringe body defines a dosage space within the syringe between the
nozzle, interior syringe walls and the plunger seal. The dosage space has
a select dosage volume when the plunger body is positioned within the
syringe body such that the dose setting surface and hammer surface are
coplanar. The selected dosage volume may be any suitable amount, for
example, 0.5 ml.

[0020] The needle-free syringe system may optionally further include a
handle substantially opposite the plunger body, a separable shaft between
the plunger body and the handle, and a break line defined in the
separable shaft. In this alternative, the break line defines the hammer
surface on the plunger body. In addition, the handle may include a
plunger positioning surface which cooperates with the hammer surface to
position the plunger body in a needle-free syringe body such that the
dose setting surface and hammer surface are coplanar. The plunger
positioning surface may define a hole providing a clearance for any nub
formed in the hammer surface upon separation of the plunger body from the
handle at the break line.

[0021] The needle-free syringe system may further include a filling
adapter. The filling adapter mates with the syringe body for filling
operations. A fluid tight seal between the adapter and syringe body may
be made by providing either the filling adapter or the syringe body with
a female conical surface and providing the other of the syringe body or
filling adapter with a corresponding male conical surface. The
corresponding male and female conical surfaces form a fluid tight seal
upon the attachment of the filling adapter to the nozzle end of the
syringe body without the requirement of a separate compliant sealing
member such as an o-ring.

[0022] The needle-free syringe system may also include a cap having an
open ended cap body size to engage and protect the nozzle end of the
syringe body and an annular flange at a closed end of the cap body which
provides a stand surface having a diameter greater than the diameter of
the open end of the cap body.

[0023] An alternative embodiment disclosed herein is a plunger and handle
system for any needle-free syringe as described above. Another
alternative embodiment is a filling adapter for any needle-free syringe
system as described above.

[0024] Another embodiment is a method of operating a needle-free injector.
The method includes providing a needle-free injection device according to
one of the alternative embodiments described above. The method further
includes activating the activation button to lock the inner housing in
the syringe loading position and subsequently loading a needle-free
syringe into the injector. An operator may then release the activation
button and move the inner housing to the firing position by pressing the
nozzle end of the needle-free syringe against the injection site with
sufficient force. The injection may then be triggered by activating the
activation button when the inner housing is fully in the firing position.
Optionally, the method may include steps of loading and ejecting a needle
free syringe from the device. Loading and ejection may occur without
touching the syringe at any time.

[0025] An alternative embodiment is a method of filling a needle-free
syringe including providing a syringe body having a nozzle at one end and
a dose setting surface substantially opposite the nozzle and providing a
plunger body in sealed engagement with an inner surface of the syringe
body where the plunger body further comprises a hammer surface. The
filling method further comprises positioning the hammer surface to be
substantially coplanar with the dose setting surface.

[0026] An alternative method of filling a needle-free syringe may include
providing a filling adapter with a filling needle in sealed fluid
communication with the nozzle of the syringe body. The plunger system
including a handle as described above may be placed into engagement with
the syringe. The plunger body may then be moved forward to the nozzle end
of the syringe body. The septum of storage vial of injectable fluid may
be pierced with the filling needle. The plunger system is then withdrawn
by the handle to a position where the break line is beyond the dose
setting surface. The handle is then removed from the plunger body by
separating the shaft at the break line. Next, the plunger body may be
moved toward the nozzle by applying force against the hammer surface with
a plunger positioning surface causing the hammer surface and dose setting
surface to become coplanar. Alternatively, the dose may be set by using a
surface within the device, for example the leading edge of the hammer, to
cause the hammer surface to become coplanar with the dose setting
surface. Throughout the dose setting operation the filling adapter and
needle-free syringe remain in direct fluid communication with the storage
vial of injectable fluid, thereby allowing the precise setting of an
injection dosage without the waste of any substantial amount of
injectable fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 is an exploded perspective view of a needle-free injection
device.

[0028] FIG. 2A is a side cross-sectional view of the needle-free injection
device of FIG. 1 while the device is positioned in the syringe loading
position prior to arming the spring power source for injection and prior
to loading a needle-free syringe.

[0029] FIG. 2B is a side cross-sectional view of the needle-free injection
device of FIG. 1 while the device is positioned in the syringe loading
position but after the device has been armed for injection and after a
needle-free syringe has been mounted. FIG. 2B shows the housing lock
engaged.

[0030] FIG. 2C is a side cross-sectional view of the needle-free injection
device of FIG. 1 while the device is positioned in the firing position
immediately prior to an injection.

[0031] FIG. 3A is a top cross-sectional view of the leading end of the
needle-free injection device in the position and configuration
illustrated in FIG. 2A.

[0032] FIG. 3B is a top cross-sectional view of the leading end of the
needle-free injection device in the syringe loading position during the
process of syringe loading.

[0033] FIG. 3C is a top cross-sectional view of the leading end of the
needle-free injection device in the firing position and configuration
illustrated in FIG. 2C.

[0034] FIG. 3D is a top cross-sectional view of the leading end of the
needle-free injection device in the syringe loading position during the
ejection of a used syringe.

[0035] FIG. 4 is an exploded perspective view of a needle-free syringe and
plunger system.

[0036] FIG. 5 is a front elevation view of a plunger and handle system.

[0037] FIG. 6A is a perspective view of a needle-free syringe.

[0038] FIG. 6B is a side cross sectional view of the needle-free syringe
of FIG. 6A.

[0039] FIG. 7A is a side cross sectional view of a filling adapter.

[0040] FIG. 7B is a perspective view of the filling adapter of FIG. 7A.

DETAILED DESCRIPTION

[0041] Unless otherwise indicated, all numbers expressing quantities of
ingredients, dimensions reaction conditions and so forth used in the
specification and claims are to be understood as being modified in all
instances by the term "about".

[0042] In this application and the claims, the use of the singular
includes the plural unless specifically stated otherwise. In addition,
use of "or" means "and/or" unless stated otherwise. Moreover, the use of
the term "including", as well as other forms, such as "includes" and
"included", is not limiting. Also, terms such as "element" or "component"
encompass both elements and components comprising one unit and elements
and components that comprise more than one unit unless specifically
stated otherwise.

[0043] FIG. 1 is an exploded perspective view of a needle-free injection
device 10. The representative needle-free injection device 10 is further
illustrated in the front elevation cross-section views of FIGS. 2A-2C and
FIGS. 3A-3D. The views of FIGS. 2A-2C and FIGS. 3A-3D show the
needle-free injection device 10 in various operational states as
described in detail below. The needle-free injection device 10 includes
an outer housing 12 and an inner housing 14. Although the outer housing
12 and inner housing 14 are shown separated into two halves in FIG. 1,
this is a non-limiting fabrication choice. The housings may be fabricated
from any suitable material in any number of sub-components provided the
housings operate with respect to each other as described herein. In the
embodiment illustrated in FIGS. 1-3, the outer housing 14 defines the
exterior of a substantially cylindrical needle-free injection device
which is conveniently sized for hand-held use. Both the device 10, outer
housing 12 and inner housing 14 are described herein as having a leading
end 16 which is defined as the injection end of the device generally
associated with a needle-free syringe (see for example FIG. 2B). In
addition, the device housings and syringe are described herein as having
a trailing end 18 substantially opposite the leading end 16.

[0044] The foregoing position and shape descriptions are provided for
convenience only and do not create any limiting configuration. For
example, the needle-free injection device 10 is illustrated herein as
being substantially cylindrical and sized for convenient hand-held use.
The various features, elements, components and methods described herein
are however applicable to other shapes, sizes and configurations of
device. Thus, terms such as leading end and trailing end are provided
merely to aid in the description of the representative embodiment and are
not intended to limit the scope of any claimed embodiment.

[0045] As shown in FIGS. 2A-2C, the inner housing 14 is movable within the
outer housing 12 between a syringe loading position and a firing
position. In particular, FIG. 2A shows the device 10 in a storage
configuration prior to or after use. FIG. 2B shows the device 10 with a
needle free syringe 20 installed. Both FIGS. 2A and 2B illustrate a
needle-free injection device 10 with the inner housing 14 positioned in
what is defined herein as the syringe loading position. In FIGS. 2A and
2B it may be noted that the inner housing 14 is positioned toward the
leading end 16 of the device with respect to the outer housing 12. This
configuration is specifically the syringe loading position of this
particular embodiment. More generally, a syringe loading position is
defined for any device as a configuration between inner and outer
housings where syringe loading or syringe ejection is enabled and
injection is substantially prohibited.

[0046] In addition, for any configuration of device, a firing position is
defined as a configuration between inner and outer housings where
injection is enabled. As discussed in detail below the safety and
efficiency of a device may be enhanced by providing distinct syringe
loading and firing configurations. FIG. 2C illustrates the needle-free
injection device 10 in the firing position, for this embodiment. In
particular, FIG. 2C shows the inner housing 14 positioned within the
outer housing 12 toward the trailing end of the device. As described in
detail below the movement of the inner housing from a syringe loading
position to a firing position provides numerous safety and injection
reliability advantages. It should be noted that the specific
configurations of FIG. 2 are not limiting. As described above, other
configurations or relationships between an inner housing movable with
respect to an outer housing could define different syringe loading
positions or firing positions for an alternative device configuration.

[0047] The needle-free injection device 10 also includes an activation
button 22 operatively associated with both the outer housing 12 and inner
housing 14. As described in detail below, the activation button 22 may be
configured to activate various device functions depending upon the
positional relationship between the inner housing 14, outer housing 12
and other elements of the needle free injection device 10.

[0048] It may be desired in selected embodiments to provide a housing lock
24 which prohibits movement of the inner housing 14 with respect to the
outer housing 12. For example, a housing lock 24 may provide safety by
prohibiting movement of the inner housing 14 from the syringe loading
position to the firing position during a syringe loading procedure. In
the embodiment of FIG. 2A-2C, the housing lock 24 may be engaged by
depressing the activation button 22 while the device is in the syringe
loading position. In particular, as shown in FIG. 2B, the activation
button 22 may include an engagement surface 26 which, when the button 22
is depressed, mates with a corresponding recess 28 to prohibit movement
of the inner housing 14 toward the trailing end of the device, thus
locking the device in the syringe loading position. The inclusion of a
housing lock 24 minimizes the risk of inadvertently firing the
needle-free injection device 10 during preliminary procedures such as
syringe loading.

[0049] The needle-free injection device 10 illustrated in FIGS. 1-2 also
includes a hammer 30 configured to drive a syringe plunger 32 forward
providing for an injection. In the embodiment of FIGS. 1 and 2 the hammer
30 is energetically driven toward the plunger 32 by energy previously
stored compressing a main spring 34. Main spring 34 is shown in an
un-compressed state in FIG. 2A and compressed in FIG. 2B. It is important
to note that the embodiments disclosed and claimed herein are not limited
to needle-free injection devices 10 which rely upon a spring for
injection power. The elements, components and methods described herein
could be implemented in a pneumatic device, an electronically driven
device or any other type of needle-free injector. Thus, in alternative
embodiments the main spring 34 could be replaced with a compressed gas
source, pneumatic chamber, a motor, an electromagnet or other power
source.

[0050] The device embodiment of FIGS. 1-2 further includes a release
mechanism 36 operatively associated with the hammer 30 such that the
release mechanism 36 can be activated to initiate the release of energy
stored in the main spring 34 to power the hammer 30 and thereby cause an
injection. In the particular embodiment illustrated in FIGS. 1-2 the
release mechanism 36 includes a lever 38 and ball lock sleeve 40 which
cooperate to releases the hammer 30 when the lever is articulated by the
activation button 22. Comparison of FIG. 2B with FIG. 2C shows that the
lever 38 is intentionally not in mechanical communication with the
activation button 22 until such time as the inner housing 14 is moved
from the syringe loading position to the firing position. Thus, the
activation button 22 cannot fire the device unless the device is in the
firing position. Therefore, the single activation button 22 may be
depressed to lock the inner housing during loading procedures in the
syringe loading position or alternatively depressed to fire the device
when the inner housing has been moved to the firing position. The
configuration of the housing lock 24 and release mechanism 36 guarantee
that the activation button 22 can only perform the appropriate function
at the appropriate time based upon the positioning of the inner housing.

[0051] The specific embodiment illustrated in FIG. 2 accomplishes firing
by the articulation of the lever 38 with the activation button 22 while
the inner housing is in the firing position as shown in FIG. 2C. The
lever 38 rotates around a pivot 42 and pushes the ball lock mechanism 40
toward the trailing edge of the device. When the ball lock mechanism 40
is moved back a suitable distance, ball bearings 44 are released from a
notch 46 in the hammer 30 and forced into channels 48 of the ball lock,
thus releasing the hammer 30 to power an injection. It is important to
note that any alternative triggering mechanism which is suitable for
articulation by the activation button 22 may be used to implement or
cause the firing of the device.

[0052] The ability of the functional elements of the needle-free injection
device 10 to enhance the safety and reliability of an injection in both
the syringe loading position and firing position are described in
additional detail below. Initially, it may be noted that the device 10
includes a skin tensioning spring 50 positioned between the outside
trailing end of the inner housing 14 and the inside trailing end of the
outer housing 12. The skin tensioning spring 50 element may be
implemented with a compression spring which has a relatively lower spring
constant than the main spring 34. Alternatively, other compression
elements such as elastomeric rings or wave washers could be used to
implement the skin tensioning spring 50. The skin tensioning spring 50
installed as shown in FIGS. 2A-2C will bias the inner housing 14 toward
the syringe loading position.

[0053] As described above, the activation button 22 may be used to engage
a housing lock 24 locking the inner housing 14 into the syringe loading
position for syringe loading or other pre-injection tasks. Prior to an
injection the housing lock 24 may be released and the nozzle end 52 of a
needle-free syringe 20 placed against a patient's skin at the injection
site. It is important for both safety and injection consistency that the
patient's skin be placed under appropriate tension prior to the
needle-free injection. Appropriate skin tension is accomplished in the
needle-free injection device 10 as force against the skin by the nozzle
end 52 is transferred through the syringe 20 to the inner housing thereby
causing the inner housing to move toward the firing position and
compressing the skin tensioning spring 50. Thus, as shown by comparing
FIGS. 2B and 2C, compression of the skin tensioning spring 50 occurs in
conjunction with movement of the inner housing 14 toward the firing
position. Furthermore, compression of the skin tensioning spring 50
requires the operator to press the nozzle end 52 of the syringe against
the patient's skin with an appropriate force. The operator is holding the
outer housing 12 during an injection so the physical act of pressing the
nozzle end 52 against the patient's skin with sufficient force causes the
configuration of the inner housing 14 with respect to the outer housing
12 to move from the syringe loading position to the firing position.
Since the skin tensioning spring resists this movement, appropriate
injection site skin tension is tunable for different situations by
selecting an appropriately sized skin tensioning spring 50 or providing
an adjustable spring pre-load.

[0054] As shown in FIG. 2A the needle free injection device 10 will
typically be delivered to an end user without a needle-free syringe 20
attached. As described in detail below, a user may fill multiple
needle-free syringes 20 with an injectable fluid in advance, possibly at
a remote location away from the needle-free injection device 10. Advance
preparation of multiple needle free syringes 20 facilitates large
inoculation projects for example.

[0055] Thus, the needle-free injection device 10 is configured to
efficiently and accurately receive, hold and eject a needle-free syringe
20. The installed needle-free syringe 20 may be selected from a supply of
prefilled syringes. In addition it may optionally be desirable that a
syringe can be mounted and ejected without touching the syringe body with
an operator's hands to minimize the risk of syringe contamination or
operator injury. Accordingly, the needle-free injection device 10 may
include a syringe mount 54, an interlocking structure 56, and an ejection
mechanism 58 which separately or together enhance several aspects of the
safe use of the device.

[0056] For example, as shown in the top cross sectional views of FIGS.
3A-3D the needle-free injection device 10 may include a syringe mount 54
comprising a socket 60 sized to receive a suitable needle-free syringe
20. Pawls 62 or a similar grasping or locking structure may be provided
adjacent to the socket and configured to positively grip an appropriate
grip surface 64 on a needle-free syringe 20. It may be noted from FIG. 3B
which shows a needle-free injection device 10 in the syringe loading
position while a syringe is in the process of being loaded that the
trailing end of the syringe 20 is received in an ejection sleeve 66 and
an ejection spring 68 is compressed. The ejection sleeve 66 and ejection
spring 68 facilitate the optional hands free ejection of a syringe as
described below.

[0057] The safe and efficient use of the needle-free injection device 10
may be further enhanced if the device is provided with an interlocking
structure 56 which prevents the placement of a needle-free syringe 20
into an engagement with the syringe mount 54 unless the inner housing 14
is in the syringe loading position. Alternatively, or in addition to this
functionality, the interlocking structure 56 may prevent removal of a
needle-free syringe 20 unless the inner housing 14 is also in the syringe
loading position. One representative and non-limiting example of an
interlocking structure 56 may be viewed in FIGS. 3A-3D and includes at
least one tab 70 on an outer perimeter surface of a pawl 62. The tab 70
corresponds with an opening 72 defined by the inner housing 14 and a
corresponding open area 74 within the outer housing 12 such that the tab
70 may extend through the opening 72 into the area 74 when the pawls 62
rotate outward and extend over the trailing end of a suitably shaped
needle-free syringe 20. FIG. 3B in particular shows the tab 70 extending
through the opening 72 and into the area 74 as a needle-free syringe 20
is in the process of being mounted.

[0058] In addition, as shown in FIG. 3D the tab 70 may extend through the
opening 72 into the area 74 when the pawls 62 rotate outward as an inner
release mechanism 76 is articulated by an eject button 78. Several safety
and efficiency attributes are provided by the interlocking structure 56
because the tab 70 will only correspond with the open area 74 within the
outer housing 12 when the inner housing 14 is in the syringe loading
position. Any possibility that the tab 70 might extend beyond the inner
housing when the inner housing is positioned away from the syringe
loading position is prohibited by providing the outer housing 12 with one
or more abutment surfaces 80 which prevent a tab 70 from extending beyond
the outer surface of the inner housing 14 if the inner housing 14 has
moved to or toward the firing position. See for example FIG. 3C which is
a top plan cross section view of the device in the firing position. Thus,
the interface between tab 70 and abutment surface 80 prevents inadvertent
ejection of a syringe in either the firing position or in an intermediate
position between the syringe loading position and the firing position.

[0059] Furthermore, an improperly loaded syringe will prevent the pawls 62
from rotating into secure contact with the grip surface 64 of a
needle-free syringe 20. Thus, an improperly loaded syringe will cause tab
70 to extend into the open area 74 within the outer housing 12.
Accordingly, a device with an improperly loaded syringe cannot have the
inner housing moved into the firing position because tab 70 will
interfere with abutment surface 80, preventing movement of the inner
housing toward the trailing end of the device.

[0060] Referring back to FIG. 2C which shows a loaded needle-free
injection device 10 in the firing position, it may be noted that
supplemental safety may be provided by including an extension 82 on the
outer housing that fully or partially shields the eject button 78 when
the inner housing 14 is moved from the syringe loading position toward
the firing position.

[0061] The syringe ejection spring 68 may be selected to provide enough
force to completely eject a spent needle-free syringe 20 from the device
10 without requiring a user to touch the needle-free syringe.
Alternatively, a device can be configured to only partially release a
syringe which may then be manually removed.

[0062] FIG. 4 is an exploded perspective view of a needle-free syringe 20
and syringe plunger system 83 showing certain enhancements. In
particular, the needle-free syringe 20 may include at least two raised
surfaces 84 defining at least one orientation channel 86 on the body of
the needle-free syringe, typically at the trailing end. The orientation
channel 86 is sized and configured to engage with corresponding syringe
orientation guides 88 which are best viewed in FIG. 3A in association
with the interior surface of the syringe mount socket 60. Thus, a user
may install a needle-free syringe 20 by sliding one or more orientation
channels 86 over corresponding orientation guides 88 until the pawls 62
engage with the syringe grip surface 64. Therefore, a syringe may be
installed and locked for use without requiring the syringe body to be
twisted as is necessary with conventional bayonet or screw type syringe
mounts. Referring back to FIG. 4, the needle-free syringe 20 may also
include visual indicia 90 which are illustrated as small raised portions
but which could be implemented with any visually observable marker. In
use the visual indicia are placed in a visually identifiable position
relative to or concealed by the leading end of the socket 60 thereby
providing visual confirmation that a syringe 20 is properly installed.

[0063] As noted above, it may be most convenient to remotely prepare
multiple needle-free syringes 20 for use with the needle-free injection
device 10. For example, one operator could be loading needle-free
syringes with an injectable fluid while another operator installs the
needle-free syringes into the device and performs injections. Remote
filling to a proper pre-determined dosage is facilitated by providing a
plunger system 83 which includes a plunger body 32 and a seal 92 sized to
fit in fluid-tight engagement with the interior chamber of the syringe,
thereby defining a fluid receiving dosage space 94 within a needle-free
syringe 20. As shown in FIG. 5, the plunger system 83 also may include a
handle 96. The handle 96 may be conveniently separated from the plunger
body 32 at a break line 98 defined in a separable shaft 100 between the
plunger body 32 and handle 96. In use the handle 96 and separable shaft
100 are typically broken away from the plunger body at the break line 98
after the syringe is filled, but before it is loaded into a device 10.
Upon removal of the handle 96 and separable shaft 100, the trailing end
of the plunger body 32 defines a hammer surface 102 which in use engages
with the hammer 30 during an injection.

[0064] As shown in FIGS. 2B and 6A-6B, the interior portion of the syringe
20 defines a dosage space 94 within the interior walls of the syringe
between the nozzle 104 and the plunger seal 92. This dosage space 94 may
be sized and configured to have a pre-selected injectable fluid dosage
volume when the plunger body 32 is positioned within the syringe such
that the hammer surface 102 is placed in a pre-defined spatial
relationship with a dose setting surface 106 on the trailing edge of the
syringe, substantially opposite the nozzle 104. For example, the dosage
space 94 may be sized to have a specific volume, for example 0.5 ml, when
the hammer surface 102 is coplanar with the dose setting surface 106.
This particular configuration is illustrated in FIGS. 2B and 2C.

[0065] As shown in FIG. 2B, the hammer 30 may be used to automatically
position the plunger body 32 such that the hammer surface 102 and dose
setting surface 106 are coplanar. It may also be noted that the leading
edge of the hammer 30 includes a recess 108 which provides clearance for
any extension or nub remaining beyond the hammer surface when the
separable shaft 100 is removed from the plunger body 32 at the break line
98.

[0066] Proper dose setting may also be accomplished in the absence of the
needle-free injection device 10 by using the plunger positioning surface
110 associated with the handle 96 to manually position the hammer surface
102 to be coplanar with the dose setting surface 106. The plunger
positioning surface 110 may, as shown in FIG. 5, include a hole 112 which
provides clearance for any extension or nub formed in the hammer surface
102 upon separation of the plunger body 32 from the handle 96 at the
break line 98. Thus, during a remote filling operation, a user may insert
the plunger body 32 and attached handle 96 fully into a needle-free
syringe 20 such that the leading end of the plunger body 32 is in contact
with the interior surface of the nozzle 104. The nozzle 104 may be placed
in fluid communication with a supply of injectable material. The handle
96 may be then be used to withdraw the plunger body 32 to a point where
the hammer surface 102 extends beyond the dose setting surface 106 of the
syringe, thereby slightly over-filling the syringe. The handle 96 and
separable shaft 100 may then be removed at the break line 98 and the
hammer surface 102 and dose setting surface 106 made to be coplanar (thus
precisely setting the selected dosage) by pressing upon the hammer
surface 102 with the plunger positioning surface 110 of the handle. The
foregoing operation may be performed while the nozzle 104 is continuously
maintained in sterile fluid communication with an injectable substance
supply, thus minimizing waste.

[0067] The remote filling of a needle-free syringe 20 may be facilitated
by providing a filling adapter 114 as shown in FIGS. 7A-7B. The filling
adapter 114 may include a male or female conical attachment surface 116
as illustrated in FIG. 7A. This conical attachment surface 116 is
configured to mate with a corresponding male or female conical surface
118 positioned at the nozzle end 52 of a needle-free syringe 20 as shown
in FIG. 6B. Thus, the corresponding male and female conical surfaces 116,
118 form a fluid tight seal upon attachment of the filling adapter to the
nozzle end of a syringe without the use of any separate compliant sealing
member, an o-ring for example.

[0068] It may further be noted from FIG. 7B that the ergonomic use of the
filling adapter 114 may be enhanced by providing stability wings 120
which provide a safe grip surface and substantially protect a filling
needle 122 from contamination.

[0069] Returning to FIG. 4 it may be noted that the needle-free syringe 20
may be provided with a cap 124 sized to engage the nozzle end 52 of the
syringe body. The cap 124 may be provided with an annular flange 126 at
the closed end of the cap providing a stand surface with a diameter
greater than the diameter of the open end of the cap body. In use, the
stand surface may be employed to stand an array of filled needle-free
syringes 20 upright in a ready position for engagement with a needle-free
injection device 10. Thus, if desired a needle-free syringe 20 may be
loaded and ejected in an efficient hands free manner.

[0070] Alternative embodiments include methods of operating and filling a
needle-free injector as described above. For example, one method includes
providing a needle-free injection device 10 according to any one of the
alternative embodiments described herein. The method further includes
activating the activation button 22 to lock the inner housing 14 in the
syringe loading position and subsequently loading a needle-free syringe
20 into the injector. An operator may then release the activation button
22 and move the inner housing 14 to the firing position by pressing the
nozzle end 52 of the needle-free syringe 20 against the injection site
with sufficient force. The injection may then be triggered by activating
the activation button 22 when the inner housing is fully in the firing
position. Optionally, the method may include steps of loading and
ejecting a needle free syringe 20 from the device. Loading and ejection
may occur without touching the syringe at any time.

[0071] Another alternative embodiment is a method of filling a needle-free
syringe 20 including providing a syringe having a nozzle 104 at one end
and a dose setting surface 106 substantially opposite the nozzle 104. The
method further includes providing a plunger body 32 in sealed engagement
with an inner surface of the syringe 20 where the plunger body 32 further
comprises a hammer surface 102. The filling method further comprises
positioning the hammer surface 102 to be substantially coplanar with the
dose setting surface 106.

[0072] An alternative method of filling a needle-free syringe may include
providing a filling adapter 114 with a filling needle 122 in sealed fluid
communication with the nozzle 104 of the syringe body. A plunger system
83 including a handle 96 as described above may be placed into engagement
with the syringe 20. The plunger body 32 may then be moved forward to the
nozzle end of the syringe body. The septum of storage vial of injectable
fluid may be pierced with the filling needle 122. The plunger system 83
is then withdrawn by the handle to a position where the break line 98 is
beyond the dose setting surface 106. The handle 96 is then removed from
the plunger body 32 by separating the shaft 100 at the break line 98.
Next, the plunger body 32 may be moved toward the nozzle 104 by applying
force against the hammer surface 102 with a plunger positioning surface
110 causing the hammer surface 102 and dose setting surface 106 to become
coplanar. Alternatively, the dose may be set by using a surface within
the device, for example the leading edge of the hammer 30 to cause the
hammer surface to become coplanar with the dose setting surface.
Throughout the dose setting operation the filling adapter and needle-free
syringe remain in direct fluid communication with the storage vial of
injectable fluid, thereby allowing the precise setting of an injection
dosage without the waste of any substantial amount of injectable fluid.

[0073] Various embodiments of the disclosure could also include
permutations of the various elements recited in the claims as if each
dependent claim was a multiple dependent claim incorporating the
limitations of each of the preceding dependent claims as well as the
independent claims. Such permutations are expressly within the scope of
this disclosure.

[0074] While the embodiments described herein have been particularly shown
and described with reference to a number of possible variations, it would
be understood by those skilled in the art that changes in the form and
details may be made to various components or elements without departing
from the spirit and scope of the embodiments and that the various
embodiments disclosed herein are not intended to act as limitations on
the scope of the claims. All references cited herein are incorporated in
their entirety by reference.